There were 14, possibly 19, major aqueducts built to serve Rome and the surrounding area. Of these fourteen, five were side channels of the major nine. These nine include, in chronological order: The Appia , built in 312 B.C., Anio Vetus, Acqua Marcia, Aqua Tepula, Aqua Iulia, Aqua Virgo, Aqua Alsietina or Agusta, Aqua Claudia and the Aqua Anio Novus. The older Aquifers received their flows from springs at the Upper Anio Valley or the Alban Hills. Later the aqueducts received water from the lower elevation springs or the Anio river itself. Consequently, as time went on the quality of the water decreased as fresh locals ran out.
Curatoreship of the aquifers was a highly sought after position. It was often considered a guarantee to a later consulship and bestowed great prestige to the incumbent. The organization of the staff of the imperial water board was as follows: The Curatore, or president,two technical advisors called adiutores , the procurator, in charge of funding, and the aquarii, or general staff. In addition an Architect, two Lictors, three Servi publici and a handful of other staff were assigned directly to the curatore and adiutores. There were no set terms of office for the upper echelons of the structure and the Aquarii tended to be slaves or freedmen before citizens. The vast majority of the work was done by contractors and only specific jobs were preformed by the administration. The bureaucracy oversaw, the civilians did the work.
The actual discharge of the aqueducts is disputed by many historians. This is due to basic errors in the Roman methods of measuring flow rates in their system. The most accepted figures are by the prominent Curatere Frontinus which cover the aqueducts present during his stay in office. The discharge, of the previously mentioned aqueducts , excluding the Aqua Tepula, totals 24,360 Quinariae, which converted to modern scales equals 2,570 gal./sec. , 222,237,060 gal./day or 1,010,623,m.3/day. These are rough figures and probably will never be proven but the vast load of the aqueducts is impressive, especially when the historical period is involved.
Selection of the springs to be used for the aqueducts, was a very important step in the construction of an aqueduct. In order to be classified a pure source, the springs had to meet strict criteria imposed by the bureaucracy. The spring first must be visibly pure and clear. It must be inaccessible to pollution and the spring itself must be free of moss and/or reeds to be viable. The local inhabitants must show no sign of diseases caused by impure water and the water must be free from foreign bodies at the spring. As for the water itself must have good sparkle, pour easily and exhibit rapid boiling. If these requirements were met then the spring was considered safe for use in the aqueduct.
When planning the course of an aqueduct the most direct route with the lowest gradient was strived to be achieved. Roman aqueducts flowed on the surface in ditches, across valleys and gradient changes in the raised stone works called piers or under the ground in tunnels in the bedrock. Unfavorable terrain was bypassed or breached according to the prices involved in the process. Limits were imposed on depth of tunnel or height of piers due to cost restrictions. If it cost too much, another route was chosen.
The acquisition of land was a major undertaking for the builders of the aqueducts. Roman officials could not compel unwilling land owners to sell their land for the aquifers. Many aqueducts were delayed immensely as officials parleyed with an adamant land owner, or waited for him to die in some cases. Once the land was obtained however it conformed to a standard pattern. On above ground courses the required tract was 15 Roman feet to each side of the structure and on below ground structures, taking 5 feet for itself, it was 5 feet. The latter boundary also applied with in the cities. No trees or structures of any type were allowed within the boundaries but grass crops or grazing were permitted. Boundaries were marked with stones called cippi and thus served as legal delimiters of adjacent growth.
The actual surveying and grading was preformed by contractors using three major instruments: the dioptra, which measured horizontal angles by sighting on a leveling staff, the libra, a simple water level, and the chorobates, a twenty foot long water level that was adjusted with plumb lines or smaller water levels. Using these tools the Romans constructed their aqueducts with an average grade of 2%. The key word is "averaged", for the grade varied greatly along its length, but it shows the great accuracy for which the Romans were famed for in their architecture.
Regular inspection was necessary for the proper upkeep of the aqueducts. shafts called pueti were drilled at interval into the tunnels for easy access. During this time they were cleaned of debris and calcification from the mineral rich water. Above ground, damage from frost, heat expansion and wind stress were major problems. Later in their lives, structural overload of the piers was common place requiring extensive buttressing and repair. The maintenance of the aquifers posed a major cost to the localities served by them. This complicated the already poor economic situation associated with the aqueducts and added to the confusion in the system as will be explained later.
Once the water reached the cities it was distributed into three sectors: Public baths, public basins and the private sector. Surplus water in the public baths and basins overflowed into the sewers and flushed the system or supplied agricultural means. In addition , low quality water from low elevation aqueducts also was put to these purposes. Pressure systems, for local use, appear at their only spot in the system here as the aqueducts flowed into large retention basins on the city walls for distribution. Finally private pressure wells were formed as water wheel pumps moved water into elevated storage tanks. The final culmination of the complex aqueduct, was the formation or a system whose complexity dwarfs that of its provider.
Throughout their Roman lifetimes, no attempt made to balance the aqueduct budgets. Original funding for the project were derived from the war spoils brought back from Rome's victorious generals. When the spoils disappeared, along with the rich countries to be conquered, taxpayers were hit hard, with no returns derived from the mis managed system. The author of my source sums the situation nicely with the quote. "The whole system was sterile and unproductive of sound prosperity as it is possible to conceive." The lack of funds was the main downfall of the aqueducts before the fall of Rome.